Most of us already know to ask for generic medicines rather than brand-name drugs. But how can you find the cheapest MRI or CT scan?

The cost of common medical procedures can vary by thousands of dollars in Houston. Patients — and the companies that subsidize their health insurance plans — can save thousands of dollars if they know which in-network hospitals, outpatient clients or lab offer the lowest prices.

But patients don't typically have access to that pricing information in advance, or even know that prices vary. Insurance contracts are confidential, and individual bills are determined by billing codes few patients understand.

Consumers can compare prices when they're shopping for a car or buying groceries, but they don't have that transparency when buying health care services, said Christopher Fisher, chief innovation officer of BenefitSpecialists, which designs benefit programs for Houston-area employers.

“If a gallon of milk is $3 in one store and $15 in another store 10 miles away, you'd think that's crazy,” Fisher said. “But that's what is going on in our health care system.”

Fisher pointed to data calculated by Compass Professional Health Services in Dallas that shows the cost for the same CT brain scan ranges from $128 to $869 among four health care providers in Houston. The company uses actual claims data from its members to build its database.

Pricing information available from insurance companies varies. UnitedHealthcare, for example gives consumers a broad, general range on what they can expect to pay for tests and to treat specific diseases.

The cost to treat breast cancer, for example, ranges from $14,411 to $19,580 for several doctors whose offices are within a 10-mile radius of Meyerland in southwest Houston, according to UnitedHealthcare's Web site. An MRI of the shoulder or arm ranges in price from $611 to $890. For specific prices, patients should ask their doctors, said UnitedHealthcare spokeswoman Kim Whitaker in Plano.

Aetna, by contrast, provides members with actual contracted rates for about 35 non-emergency procedures, including CT scans, MRIs, biopsies and colonoscopies.

It's real-time data updated daily, said Wayne Gowdy, senior product manager in product development for Aetna, based in Hartford, Conn.

Prices for an MRI of the back at 37 facilities close to Bellaire range from $425 at a free-standing diagnostic center to a range of $1,629 to $2,139 at one of Houston's hospitals.

Patients paying more

Free-standing imaging centers generally charge less than hospitals, said Gowdy, who asked the Houston Chronicle not to identify the names of the specific providers because the list of prices is available only to Aetna members.

With third parties picking up much of the bill, health care consumers haven't had much incentive to compare prices. But as deductibles and co-pays go up and consumer-directed health savings accounts gain popularity, patients are footing more of the bill themselves. The accounts are tax-advantaged and must be tied to a high deductible health plan, giving consumers a reason to pay close attention to what they're spending.

Many patients mistakenly assume the prices are the same, said Eric Bricker, chief medical officer for Compass Professional Health Services.

Compass, which started in 2007, has signed up 62 client companies that use its price comparison data. Clients provide their claims data and from that, Compass pulls out the prices for a range of medical procedures at different outpatient surgical or diagnostic centers and hospitals.

Bricker, who is still a practicing hospital physician, said he launched the company when he saw patients struggle with costs. One of his hospital colleagues, an orthopedic surgeon, began giving his patients the billing codes for MRIs and suggested they shop around.

Bricker estimates that comparison shopping saves the average employee about $620 per year. With a self-funded plan — which most large companies have — about half of that savings goes to employees and the other half goes to the employer.

Even people who consider themselves knowledgeable have been stunned to discover prices can vary so widely inside their insurance networks.

“Jaws dropped all around the room,” recalled Bruce Whitaker, president of the Whitaker Companies, a professional staffing firm based Houston, who along with his 75 employees heard a presentation from Fisher on how to compare prices. He is not related to the UnitedHealthcare spokeswoman. His company's services include placing physicians in short-term assignments.

“We're inside the community,” he said. “We should know better.”

‘I had no control'

Patrick Montesanto, a recruiter for Bruce Whitaker's information technology division, used to focus just on his co-pays. But since he signed up for his company's high deductible health savings account, he's had to pay much closer attention to prices. He found out how difficult it is to determine the cost up front.

Montesanto needed knee surgery, so he made sure in advance that the imaging facility was in his insurance network and the price was reasonable. But when the bill arrived, he got a surprise — the radiologist who read the MRI was not in the network.

“Through no fault of my own, I got a bill for the full charge of reading the MRI — it was several hundred dollars,” he said. “I had no idea. I had no control.”

Then it turned out the surgical portion was in-network but the anesthesiologist was not, said Montesanto, who was charged the full out-of-network price.

He estimates he has spent 80 to 100 hours trying to sort out the billing.

“I haven't paid a dime,” he said, sticking to his contention that he had no control — and no knowledge — of the behind-the-scenes service providers even though he thought he had done his homework.

“Transparency doesn't exist until they're trying to stick you with the bill,” he said.

Aetna, with about 1 million members in Houston, has begun including those behind-the-scenes providers in its price estimates, based on two years of claims.

It launched the pricing program in 2004 and has rolled it out to 80 percent of its market. Gowdy said the Web-based estimator gets more than 61,000 hits a month.